Both patch or “microstrip” antennas and monopole antennas are well established in the art. Patch antennas typically provide antenna beam patterns with a peak gain in a direction perpendicular to the plane of the patch, but have increasingly lower gain in directions at increasing angles to this perpendicular direction, resulting in an antenna beam pattern with a generally teardrop shape when depicted in three dimensions. Monopole antennas provide antenna beam patterns having a peak gain in directions between a line through their axes and those perpendicular to this axial direction, which when depicted in three dimensions appears somewhat toroidal.
Combining a patch antenna with a monopole antenna to produce a composite antenna beam pattern has been proposed in a specific context using exclusively linear polarization in both antennas. According to the proposed design, a monopole antenna extending perpendicularly along a z axis from a ground plane lying in an x-y plane is excited by a single, center feed to produce an antenna beam having polarization in the x direction, which, with z in the upward direction, constitutes horizontal polarization. A patch antenna lying in an x-y plane above the ground plane is excited by a single feed, off-center in the x-y plane (along the y axis). The objective of this specific configuration is to produce a broad-beam antenna pattern that exclusively exhibits a horizontal polarization in the y-z plane of interest. This design was proposed for use in an array of antennas deployed in a cellular communication base-station (cell tower) where horizontal polarization optimized in a single plane was believed to be useful.
Further, patch antennas having circular polarization are known. However, circular polarization is generally undesirable in applications where a particular linear polarization is desired, such as in the aforementioned antenna system, because circular polarization distributes half of the radio frequency (RF) energy in a perpendicular horizontal polarization, generally making signal detection more difficult in each of the linear polarizations. Thus, introduction of circular polarization in the aforementioned system optimized for horizontal polarization in a particular plane would result in poorer performance.